Dust recorder



Patented Feb. 23, 1943 DUST/.EECORDF-ll.

Vernet Dahlmanandv Arthur Nutting, Louisville,

Ky.,l assignors-toAmercan A ir Filter Company, Inc., Louisville, K-y.,a. corporation of Delaware Applicationjuly 25, 194-1,` Scrial No.404,024'.

7ffCl'aims,

To vdetermine the dust collecting or cleaningeiiiciency oan air cleaner,it has r been proposed` to connect the air ductvat opposite sides. of#the air cleaner to a sealedchamber through separate` air samplingconduits, each terminatingin @nozzle having a very small` dischargeopening spaced a minute distance from the face of a recording disc ortarget which is rotated by. suitable means at a slow constant speed,say, one revolution per day. In operation, av vacuum is createdwithinthe chamber, causinga stream of air to ilow- Y through eachsampling. conduit andto jet against therecordingjtarget, at a velocitywhich, dueto the smallness of the dischargev opening, isabove thecritical point ofi'the nozzle; hence remains constant despite minorvariationspin, the air-duct pressure. With this arrangement,all,orsubstan tially all, of the dust contained in each streamisdeposited upon the targetiforming two separate tracks, the relativedensities of which are- The present invention relates to an improved`method of, and means for, measuring the dust collectingY or cleaningefficiency of; an air cleaner.

The principal object isto; provide a novel-methodby which the eicienciesmay be determined accurately and quickly.

Another important object is to providel animproved recorderv ofg thisgeneral typev which operates to evaluate the track densities accuratelyand quicklyv in terms permitting theelciency to bev stated on a,percentage basis.

A novel f ormof; recorder constructed inv accordance .with our inventionand; capable of,I carrying out either the old method or the novel methodprepesed herein-1S illustrated in` the accompanying drawings wherein:

Figure 1 is a side View Corresponding to one taken along line I-I ofFigure 2;;

Figure 2.15 e top plan.; and,

Figure 3` isl an end View.A corresponding to one taken along line 3-f3ofFigure 2*'.

The dust recorder illustrated in the drawings conventionally includes avessel I having:` a sealed chamber 21; an observation port in the formof a glass cover `3; an evacuating nipple 4; adapted for connection to avacuum pump not shown. for exhausting the interior of the vessel` I; andfore and aftnipples 5 andA 5a. The outer ends of the fore. and aftnip/plesL 5. and; 5a are adeptedor cenneetenthreuehore and aft conduitsto an` operating air cleaner, that is to. say, an aircleaner positionedin an air duct and operating. to c lean airpassing through the ductjtheconduits, air.. cleanerAv and air duct not being shown. Theinner endsof. the fore andl aft nipples 5- and 5a,y are connectedthrough fore andaftV hoses Iir and 6a. to nozzles 1 and la Which dischargeinto thesealedt chamber.

With this arrangement, the evacuation of the s ealedchamberZwillinducefore andaft streams of. air to flow from the fore and aftsides of the air cleaner-through thefore and. aft conduits and jet intothe; chamber through the fore and aft` nozzles 1 andV 1a. As they degreeof vacuum increases from zero, when operationis first instituted,ithevelocity of each dischargekjet increases until the critical velocity isreached, at which further increasesin thedegree of vacuum willnotproduce any! further increases` in velocity. The

nozzles are. ldesignedI to have substantially equal critical points orvelocities, Whilev the degreef o f vacuum employed preferably isabovethat required to produce; the; critical velocities. Consequently, duringoperation,` the jet velocities will remain at the samerconstant valuedespite minor variations in the air pressure at the fore and aft sides.o the. air cleaner,

InE accordance with our invention, the fore and aft jets arerespectively directed1 against separate fast andslow targets 8 and 8amoving-at speedsy adjusted so that the tracks producedl on bothtargetswill be ofthe same density. By adjusting the speed of the slow=target to` bring the density of the aft track within a range in whichthe eye is. capable of quickly detecting Slight differences in shade, wehave found that the speed of thefastV target may be quicklyL fjlllstedto a value at which the shade of its fore track matches thel shade. ofthe aft track andy that, when the vtracks are` matched in this way, theratio R of the slow, to', the fast target speeds, is an accurateindication off the inefliciency of the air cleaner.

The efliciency in per centmayvbe determined byI theE following formula:100,. minus 10Q times R.

For example with a ratio of 1 to 20, the efficiency este dineherizentellr egressv theffOr-e iet Where it; isrriinutely Seated fromthe, discharge emil of 'Ehe tape is Supreme@ fer movement along thispath by means of an arm I0, having secured and free ends. The securedend is pivotally mounted upon a stand I I, while the free end isresiliently urged upwardly by means of a spring I2 which is suitablyanchored to the stand II and arranged appropriately to engage the armI0. The spring I2 functions to press an idling roller I3, which isrotationally carried by the free end of the arm I0, into yieldingengagement with a drive roller I4. The drive roller is mounted upon adrive shaft I which projects out of the vessel I through a wall thereof.In this way, when the tape is inserted between the drive and idlingrollers, appropriate rotation of the drive roller pulls the tape fromthe supply roll across the jet, thereby causing the fore track to beformed on the tape. The tape discharges from the roller into the adja-ycent space of the sealed vessel I.

The slow target 8a. is similarly arranged; hence it is associated with asupply stand 9a, arm Illa, supporting stand II (common to both targets),a spring corresponding to spring I2, idling roller I3a, drive roller I4aand drive shaft I5a, the latter likewise projecting out of the vessel I.

The drive shafts I5 and I5a may be driven by any suitable adjustablespeed means. In the arrangement shown, a motor I6 operates, through thegear reducer I1 and stepped wheels I8, to drive a disc I9. The motorreducer and stepped Wheels are adjustably mounted as a unit to permitany one of the stepped wheels I8 to be placed in peripheral engagementwith the periphery of the disc I9. In this Way, the disc may be drivenat any of a corresponding number of different constant speeds.

The shaft 20, upon which disc I9 is mounted, carries a small gear 2|which meshes with a similar gear 22 on drive shaft I5a to drive the slowtarget 8a. The fast target 8 is driven through the engagement, with theface of the disc I9, of a knurled roller 23 mounted on drive shaft I5for axial movement along the shaft and rotational movement with theshaft.

If desired, the face Iof the disc I9 may be provided With a series ofradially spaced grooves 24 dimensioned to provide denite speed ratiosbetween the drive shafts I5 and I5a. For example, the innermost groovecould be made of the same diameter as the gear 2| providing a 1 to lratio while the outermost groove might be made of a size providing a 20Ito 1 ratio. With grooves of this character, it would not be necessary tomeasure the speed of either shaft since the speed ratio would beinstantly known from the particular groove employed. Where grooves orthe like are employed, the drive shaft I5 should be made flexible inorder to facilitate the transfer of knurled roller 23 from one groove toanother. This is easily accomplished by reducing the diameter of shaftI5 as indicated at I5d although various other well-known equivalentmeans may be employed. Since shaft I5 is flexible, its projecting end isengaged by spring 25 which functions to urge the shaft laterally towardthe disc, thus pressing the roller 23 firmly against the disc.

In operation, with the fore and aft nozzles 'I and la connected to theair duct at the fore and aft sides of the air cleaner and with theinterior of vessel I vacuated through its connection with a vacuum pump,the motor I8 is started and the speed of the slow target 8a. adjustedthrough the connection between the stepped wheels I8 and the disc IS-toa constant value at? Vraft track on target 8a. When a color match isthus made, the ratio of slow to fast speeds can be readily determinedfrom the 'groove from which the knurled roller engages. With this ratioknown, the efficiency can be quickly calculated. In this way,` we havefound it possible to obtain accurate measurements of efficiency inrelatively short intervals of time.

It Willl be appreciated that if the recorder shown is set at a l to 1ratio, it may be operated to carry out the old method of determiningeniciency by ascertaining the relative densities of the fore and afttracks. This may be useful occasionally to obtain a check determinationof the efficiency.

Having described our invention, we claim:

1. In a method of measuring the efliciency of an operating air cleanerin an air duct, the steps of: removing separate streams of air from theduct at the fore and aft sides of the cleaner; jetting the streams atpredetermined rates upon separate moving targets to form fore and afttracks; adjusting the relative speeds of the targets to values at whichthe tracks formed are of substantially equal density; and determiningthe relative speeds of the fore and aft targets whereby the air cleanerefficiency may be determined.

2. In a method of measuring the efficiency of an operating air cleanerin an air duct the steps of: removing separate streams of air from theduct 'at the fore and aft sides of the cleaner; jetting the streams atsubstantially equal critical velocities upon separate moving targets toform fore and aft tracks; adjusting the relative speeds of the targetsto values at which the.

tracks formed are of substantially equal density, and determining therelative speeds of the fore and after targets whereby the air cleanerefficiency may be determined.

3. In a method of measuring the efficiency of an operating air cleanerin an air duct the steps off: removing separate streams of air from theduct at the fore and aft sides of the cleaner; jetting the air atsubstantially equal critical velocities upon separate moving targets todeposit substantially all of the dust contained in said streams uponsaid targets and thereby form fore and aft tracks; adjusting therelative speeds of the targets to values at which the tracks formed areof substantially equal density, and determining the relative speeds ofthe fore and aft targets whereby the air cleaner efficiency may bedetermined.

4. In a method of measuring the efciency of an operating air cleaner inan air duct the steps of: removing separate streams of air from the ductat the fore and aft sides of the cleaner, jetting the air atsubstantially equal critical velocities upon separate moving targets toform fore and aft tracks; adjusting the speed of the aft target tothevalue at which the aft track is of an intermediate shade havingcolor-matching quality; adjusting the speed of the other target to avalue at which the density of the.

fore track is substantially equal to that of the aft track, anddetermining the relative speeds of the fore and aft targets whereby theair cleaner efciency may be determined.

5. A dust recorder of the type having a sealed chamber adapted forconnection to an air duct at the fore and aft sides of an operating aircleaner through fore and aft sampling conduits terminating in nozzleshaving similar critical velocity characteristics, wherein the evacuationof the chamber causes fore and aft streams of air to jet atsubstantially equal critical velocities from the nozzles into thechamber comprising: fore and aft targets arranged for movement acrossthe fore.- and aft jets respectively; means for moving said targetswhereby fore and art dust tracks are formed thereon; and means foradjusting the relative speeds of said targets to values at which thefore and aft tracks are of equal densities.

6. The recorder of claim 5 wherein the adjusting means includes meansfor indicating a series of predetermined target-speed ratios.

7. 'Ihe recorder of claim 5 wherein the adjusting means includes: a discconnected to rotate in accordance with the speed of one target, the dischaving a series of concentric grooves on one face representing a seriesof known ratios between the linear speeds of the grooved portions of thedisc and the speed of said one target; and a roller connected to drivethe other target, the roller being adjustably mounted for movement alongthe face of the disc to place its periphery into driven engagement withone groove or another of said disc.

VERNER DAHLMAN. ARTHUR NUTTING.

